This invention relates generally to the field of ovens for subjecting objects to an elevated temperature for a prolonged period for the purpose of baking or cure drying coatings, such as varnish on electrical windings, or the like.
More particularly, the invention is directed to a novel, modular, varnish baking oven that is particularly suited to drying varnish or varnish-like coatings on stators or other components of electrical machinery that are difficult to remove to a remote location because of their size and configuration. For example, at times it becomes necessary to rewind the stators of rather large electrical generators used on submarines or other vessels having hatchways or access openings that are smaller than will permit passage of the components to be rewound. In these circumstances, it has been necessary either to cut an opening in the hull of the submarine or vessel large enough to remove the component to a workshop, or to rewind and varnish the component on board. The former expedient poses obvious disadvantages of cost, time, and possible loss of hull strength after repair, while attempts at the latter expedient have been notably unsatisfactory because of a lack of suitable means for baking the necessary varnish coatings on the new windings. Efforts to effect baking of the varnish with infra-red or heat lamps and jury rigged enclosures have produced poor results and windings of uncertain reliability.
A variety of oven devices that can be assembled from portable components have been devised for various purposes including drying of paints or varnishes on automobiles as taught by U.S. Pat. No. 1,352,893 to W. O. Guice. That device includes a plurality of rectangular side wall sections and top wall sections adapted to be clamped together for forming an oven enclosure around an automobile, and having an electric heater, a blower, and conduits for forcing heated air into the oven. Other ovens, for example gas fired baking ovens, have been constructed from sections designed for convenience of shipping from the point of manufacture. Examples of these are found in U.S. Pat. No. 906,251 to G. B. Meek and U.S. Pat. No. 1,426,059 to M. Froehlich.
While each of the foregoing structures meets the particular needs of the use for which it was designed, none are well suited to the peculiar situation of baking a rewound and varnished 30 KW stator on board a submarine, for example, having hatchways the diameters of which are too small to permit removal of the stator. The preferred varnish curing procedure calls for initial heating of the varnish dipped stator coupled with a substantial air flow to carry away vapors, followed by baking with a reduced air flow for a predetermined time period at a temperature in a predetermined range. This process may be repeated for successive coats.
Because the submarine itself is substantially closed and is usually occupied by crew or yard personnel, it is necessary that the on board baking be accomplished without undue heating of the workspace concerned or polution of the air therein with possibly toxic vapors. Accordingly, it is desirable to provide an oven that is well insulated and which provides for efficient controls for temperature and air flow therethrough.